A 107 kDa integral protein antigen of MAb 30B6 (also referred to as Sgp 130, reduced form of the 107 kDa species) is proposed to be a novel actin-associated plasma membrane glycoprotein which provides an anchor for vinculin and regulates or re-enforces integrin-talin transmembrane associations via direct molecular interactions with integrin. The intermolecular relationships which may exist between the 107 kDa integral protein and integrin, vinculin and talin are hypothesized to be critical in the assembly and integrity of microfilament attachments to the plasma membrane and hence of great importance co the analysis of heart morphogenesis, cardiovascular disease and the pathobiology of the transformed cell. In order to establish the molecular structure a"d function of the MAb 30B6 107 kDa integral protein, the basis for its apparent interactions with vinculin and integrin, physiological significance of tissue-specific trends in its expression and dynamic nature of its interactions with vinculin and integrin in living cells, three substantial lines of complementary biochemical, molecular biology and immunological approaches are proposed. In the first area of study, a comprehensive molecular analysis of the MAb 30B6 107 kDa integral species will be undertaken. Studies will involve HPLAC purification of the antigen, specific chemical cleavage of the protein to obtain well- defined fragments and partial sequence determination. The gene encoding the 107 kDa species will be cloned and sequenced. Monoclonal antibodies to defined molecular regions and reduced/non- reduced forms of the 107 kDa species will be developed. Several physiochemical/biophysical properties of the 107 kDa species and in vitro interactions with actin and vinculin will be analyzed. In the second area of study, biosynthetic and post-translational modifications of the 30B6 107 kDa integral species will be defined. Gene specific probes will delineate regulatory mechanisms that govern its differential expression in smooth and cardiac muscle. Other studies will highlight changes in cellular expression and topological distributions of the 107 kDa integral protein relative to vinculin and integrin, and the effects of Rous sarcoma virus transformation on these protein relationships. Cell events to be subsequently investigated will include in vitro myogenesis. In the third area of study, microinjection experiments with living embryonic chick cardiac fibroblasts and myocytes will explore the coordinate functions of the 107 kDa integral protein and vinculin in the dynamic assembly of force generating microfilament-membrane attachment sites.